Method and device for band-edge orientated displacement of intermediate cylinders in a 6 cylinder frame

ABSTRACT

A method for the strip-edge-oriented shifting of the intermediate rolls ( 11, 11′ ) in a six-roll rolling mill comprising respectively a pair of workrolls ( 10, 10′ ), intermediate rolls ( 11, 11′ ) and backup rolls ( 12, 12′ ), whereby at least the intermediate rolls ( 11, 11′ ) and workrolls ( 10, 10′ ) have devices for axial shifting cooperating with them and each intermediate roll ( 11, 11′ ) has a barrel elongated by the amount of the CVC-shifting stroke and a one sided setback (x) in the region of the strip edge. The method is characterized in that the upper intermediate roll ( 11 ) is shifted in the direction of the drive side (AS) and the lower intermediate roll ( 11′ ) is shifted in the direction of the service side (BS)—or conversely—relative to the neutral shift position (S zw   =0  mm) symmetrically to the rolling mill center (y-y) be respectively the same amount in the direction of their (x-x).

[0001] The invention relates to a method of and an apparatus for the strip-edge-oriented shifting of the intermediate rolls in a six-roll rolling mill, comprising respectively a pair of work rolls, a pair of intermediate rolls and a pair of back-up rolls, whereby at least the intermediate and work rolls cooperate with devices for axially shifting them and each intermediate roll has a barrel elongated by the CVC (continuous variable crown) shifting stroke with a one-sided setback [ground-back region] in the region of the strip edge.

[0002] The quality requirements of cold-rolled strip with respect to thickness tolerances, the attainability of certain final thicknesses, strip profiles [cross sections], strip planarities, etc. are continuously increasing in the course of developments. As a consequence of such developments, the requirements for flexible rolling mill concepts and modes of operation are always increasing more significantly and are required to be optimally matched to an end product to be rolled.

[0003] For the classical rolling mill types referred to as quarto [four-high] and [six-high] sexto mills there are aside from basic concepts with bending systems and fixed roll barrel shapes as roll gap influencing elements, two significant further rolling mill concepts which additionally affect the rolling gap by shifting of the working rolls or intermediate rolls based upon different effective principles. These are:

[0004] CVC/CVC-plus Technology

[0005] The technology of strip-edge-oriented shifting of rolls

[0006] Up to now both of these technologies have required different rolling mill concepts because different roll geometries were required for them.

[0007] In the classic CVC [continuous variable crown] technology, the barrel-shaped lengths [contour length] of the shiftable rolls was always longer than those of the fixed unshiftable rolls by the axial shifting stroke. The shiftable rolls thus need not have had their barrel terminating edge shifted beneath the stationary roll barrel. Thus surface damage or marking is avoided.

[0008] By contrast in the technology of strip-edge-oriented shifting, in the entire set of rolls, rolls with identical barrel [contour] lengths are used. The shiftable rolls are thus shaped at the one side in the barrel edge region with a corresponding geometry, especially they can be provided with a taper. As a result, locally arising load peaks can be reduced.

[0009] The effective principle depends upon the strip-edge-oriented readjustment of the barrel edge, either ahead of or at or even behind the strip edge. Especially in the case of six-roll rolling mills, the shifting of the intermediate rolls beneath the backing roll gives rise to a targeted influence on the effectiveness of the positive work roll bending.

[0010] The invention has as its object to utilize both technologies through a unitary mode of operation in a rolling mill conceptualization with geometrically identical roll sets.

[0011] To achieve this object, a method for the strip-edge-oriented shifting of the intermediate roll in a six-roll rolling mill of the kind indicated in the preamble of claim 1 is proposed in accordance with the invention in which the upper intermediate roll is shifted in the direction of the drive side (AS) and the lower intermediate roll is shifted in the direction of the service side (BS)—or conversely—relative to the neutral shifting position (S_(zw)=0 mm)), symmetrically with respect to the middle of the rolling mill by respectively the same amount in the direction of their axes.

[0012] By the use of intermediate rolls with filled setbacks [ground-back regions] and strip-width dependent optimization of the axial shifting positions, the effectiveness of the positive work roll bending can be influenced in a targeted manner. Thus the roll gap can be optimally set.

[0013] In a refinement of the process, through the shifting of each intermediate roll, the beginning of the recess is positioned externally of or at, or within the strip edge, i.e. within the strip width.

[0014] And finally, the method provides that the shifted positions in different strip width regions are given piecemeal by linear expressions [functions] which setback different positions of the beginning of the recess relative to the strip edge.

[0015] An intermediate roll for strip-edge-oriented shifting with two-sided elongated roll barrels [contours] on the two sides, especially for carrying out the method according to the invention is characterized in that they each have elongated barrels extended by the CVC stroke which is symmetrical for the neutral shift position (S_(zw)=0 mm) at the rolling mill center.

[0016] As a basis for the rolling mill concept with intermediate rolls for strip-edge-oriented shifting with two-sidedly elongated roll barrel, the roll configuration from CVC/CVC-plus-technology for a six-roll rolling mill is used.

[0017] As a refinement of the intermediate roll for strip-edge-oriented shifting with two sides elongated rolling contours provides that the barrel at the service side (BS) is provided with the setback (x) [ground back region], whose length (l) is subdivided into two adjoining regions a and b as to which the following equations apply: Region a: x = {square root}R² − (R-d)² y(x) = R − {square root}R² − (1-x)²) Region b: x = 1 − a y(x) = d = const.

[0018] As a result locally arising load peaks are reduced, as is based upon the effective principle of the strip-edge-oriented reshifting of the barrel edge, either ahead of or to or to a location behind the strip edge. Especially in the case of six-roll rolling mills, the shifting of the intermediate rolls beneath the backing rolls gives rise to a targeted influence on the effectiveness of positive work roll bending.

[0019] An intermediate roll is further characterized in that the transition between the recess (x) between the regions a or b, for example for a given length a of 100 mm is effected with a sequential setback of the measurement d in accordance with the following table:

[0020] Over a: x 10 d/512 20 d/256 30 d/128 40 d/64 50 d/32 60 d/16 70 d/8 80 d/4 90 d/2 100  d

[0021] And finally, a refinement of the rolling mill in accordance with the invention provides that the one-sided setback (x) is provided on the upper intermediate roll, preferably at the service side (BS) and on the lower intermediate roll at the drive side (AS) or inversely.

[0022] Details, features and advantages of the invention are given in the following description of several embodiments schematically illustrated in the drawing.

[0023] It shows:

[0024]FIG. 1 a geometry of the intermediate roll without the roll setback [ground-away region],

[0025]FIG. 2 a one-sided setback [ground-away region] in the region of the barrel edge of the intermediate roll,

[0026]FIG. 3 a showing of a rolling mill for strip-edge-oriented shifting with elongated intermediate roll barrels,

[0027]FIG. 4 different positions of the intermediate roll setback of the intermediate rolls.

[0028] The intermediate roll shown in FIG. 1 is derived from the roll configuration of the CVC/CVC-plus-technology for a six-high rolling mill. FIG. 1 shows a work roll 10, an intermediate roll 11 and a backup roll 12. The shiftable intermediate roll has a barrel elongated by the amount of the CVC shifting stroke which has a neutral shifting position at the center of the rolling mill defined by the plane y-y.

[0029]FIG. 2 shows a one-sided ground away region [setback] x in the region of the barrel edge 13 of the intermediate rail 11. The setback x has the length l and the barrel of the intermediate roll 11 extends from the barrel edge 13 up to the barrel center with the length B. The length of the setback x is divided into two adjoining segments. In the first segment a, the setback conforms to the circle equation

(l−x)² +y ² =R ²

[0030] If a predetermined minimal required diameter reduction 2d, dependent upon the external boundary conditions, for example, rolling force and the thereby resulting roll deformation, is reached, the setback x will run linearly up to the barrel edge 13. The diameter reduction is thus so provided that the work roll can bend freely by the amount of the setback x of the intermediate roll without a contact therewith in region b. The length l of the setback is subdivided into the regions a and b which can be calculated from the equation given in claim 5.

[0031] The transition between region a and region b can be made with or without a continuously differentiation transition.

[0032] With another transition function for a predetermined length a of 100 mm, a special setback of the dimension d resulting from the ablation [grinding away] can be effected according to the table given in claim 7. The predetermined function here is flatter in the transition region than a radius and is very much steeper at the ends. Because of reasons of grinding technology, the transition toward the cylindrical part is made with a correspondingly greater break in the transition between a and b (about 2×d).

[0033] As can be seen from FIG. 3, in the normal case, the one-sided setback is provided on the upper intermediate roll 11 at the service side BS and on the lower intermediate roll 11′ at the drive side AS, although it, however, does not change the effective principle when one applies the setback x of the upper intermediate roll 11 at the drive side AS and on the lower intermediate roll 11′ at the service side.

[0034] By the axial shifting of the intermediate rolls 11, 11′, the beginning of the setback x can be positioned outwardly to, at or inwardly of the strip edges 14, 14′ as FIG. 4 shows. This positioning is effected as a function of the strip width and material characteristics can be targeted at effectively setting a positive work roll bending. Positive shifting of the intermediate roll 11 signifies that the upper intermediate roll 11 is shifted in the direction AS and the lower intermediate roll in the direction BS as can be determined from FIG. 3.

[0035]FIG. 4 shows positioning of the intermediate roll setback with:

[0036] Shifting of the intermediate roll outside the strip edge (m=,,+”)

[0037] Shifting of the intermediate roll onto the strip edge (m=0)

[0038] Shifting of the intermediate roll within the strip edge (m=,,−”)

[0039] In different strip width regions, the shift positions is predetermined by piecemeal linear step functions which define definite positions of the beginning of the setback x relative to the strip width.

[0040] The most important advantage of the described rolling mill concept, with only one geometrically identical roll set both CVC/CVC-plus-technology of strip-edge-oriented shifting can be obtained. It is no longer necessary to have different roll types. Differences can reside only in the nature of the grinding of the rolls, however for a cvd plus- or setback x in accordance with the above-defined parameters. 

1. A method of strip-edge-oriented shifting of the intermediate rolls (11, 11′) in a six-roll rolling mill, comprising respectively a pair of workrolls (10, 10′), a pair of intermediate rolls (11, 11′) and a pair of backup rolls (12, 12′) whereby at least the intermediate rolls (11, 11′) and the workrolls (10, 10′) cooperate with devices for their axial shifting and each intermediate roll (11, 11′) has a barrel elongated by the amount of the CVC-shifting stroke wtih a one-sided setback (x) in the region of the strip edge (14), characterized in that the upper intermediate roll (11) is shifted in the direction of the drive side (AS) and the lower intermediate roll (11′) is shifted in the direction of the service side (BS)—or conversely—relative to the neutral shifting position (S_(zw)=0 mm) symmetrically with respect to the rolling mill center (y-y) by respectively the same amount in the direction of their axes (x-x).
 2. A method according to claim 1 characterized in that the shifting of each intermediate roll (11, 11′) the beginning of the setback (x) is positioned outside, or at, or within the strip edge (14), that is within the strip width.
 3. A method according to claim 1 or claim 2 characterized in that the shifting position in different strip width regions is predetermined by piecemeal linear step functions which define different positions of the beginning of the setback (x) relative to the strip edge (14).
 4. A rolling mill for strip-edge-oriented shifting of the intermediate rolls, have elongated roll barrels on both sides, especially for carrying out the method according to the invention, characterized in that the intermediate rolls (11, 11′) each have an elongated barrel extended by the amount of the CVC stroke which is disposed symmetrically with respect to the neutral shifting position (S_(zw)=0 mm) at the rolling mill center (y-y).
 5. The rolling mill according to claim 4 characterized in that the barrel of the intermediate roll (11) at the service side (BS) is provided with a setback (x) whose length (l) is divided into two multiadjacent regions (a and b) which are given in the following equations: Region a: x = {square root}R² − (R-d)² y(x) = R − {square root}R² − (1-x)²) Region b: x = 1 − a y(x) = d = const.


6. The rolling mill according to claim 4 or 5, characterized in that the transition of the setback (x) between the regions a or b, for example, for a predetermined length of 100 mm for a, with a sequential recession in the dimension d is effected in accordance with the following table: Over a: x 10 d/512 20 d/256 30 d/128 40 d/64 50 d/32 60 d/16 70 d/8 80 d/4 90 d/2 100  d


7. The rolling mill according to one or more of claims 4 to 6 characterized in that the one-sided setback (x) is preferably at the service side (BS) for the upper intermediate roll and on the drive side (AS) for the lower intermediate roll. 